Activated carbon fibers (ACF) are considered viable alternative adsorbent materials in respirators because of their larger surface area, lighter weight, and fabric form. The purpose of a recent study led by Dr. Claudiu T. Lungu, associate professor in the department of environmental health sciences at the University of Alabama at Birmingham—in collaboration with UAB alumni Dr. Jo Anne G. Balanay, assistant professor in the department of health education and promotion at East Carolina University, and Dr. Evan L. Floyd, assistant professor in the department of occupational and environmental health at the University of Oklahoma — was to characterize the breakthrough curves of toluene for different types of commercially available ACFs to understand their potential service lives in respirators.
Two forms of ACF — cloth (AC) and felt (AF) — with three surface areas each were tested. ACFs were challenged with six toluene concentrations (50 to 500 parts per million) at constant air temperature (23 degrees Celsius), relative humidity (50 percent), and air flow (16 l min-1) at different bed depths. Breakthrough data were obtained using continuous monitoring by gas chromatography using a gas sampling valve. The ACF specific surface areas were measured by an automatic physisorption analyzer.
Results showed unique shapes of breakthrough curves for each ACF form: AC demonstrated a gradual increase in breakthrough concentration, whereas AF showed abrupt increase in concentration from the breakpoint, which was attributed to the difference in fiber density between the forms. AF has steeper breakthrough curves compared with AC with similar specific surface area. AC exhibits higher 10 percent breakthrough times for a given bed depth due to higher mass per bed depth compared with AF, indicating more adsorption per bed depth with AC. ACF in respirators may be appropriate for use as protection in environments with toluene concentration at the Occupational Safety and Health Administration Permissible Exposure Limit or during emergency escape for higher toluene concentrations. ACFs have shown great potential for application in respiratory protection against toluene which was the test VOC, but potentially could be used for more toxic VOCs like benzene. The results obtained can be used in the development of thinner, lighter, and more efficient respirators.
“Breakthrough Curves for Toluene Adsorption on Different Types of Activated Carbon Fibers: Application in Respiratory Protection” was published online in the May issue of The Annals of Occupational Hygiene.
Journal article: http://annhyg.oxfordjournals.org/content/59/4/481.abstract